Evaluation support for multimodal models in NeMo 2.0

[athitten]

To verify evaluation on multi modal models, depends on NVIDIA-NeMo/Export-Deploy#423

[athitten]

@marta-sd to test with VL-EvalKit after the OAI API is added.

[athitten]

Bobby's PR is not merged yet, addressed the comments. Can get the PR merged, can fix bugs in the bug fix branch.

[athitten]

PR: NVIDIA-NeMo/Export-Deploy#440

[athitten]

PR to be cherry picked to the 25.11 branch, @marta-sd to test it out end of this week or early next week.

[athitten]

@marta-sd to try to test it out this week.